Reland r165710 "Replace RenderFullScreen with top layer"

Source/core/html/HTMLDialogElement.h

Index: Source/core/html/HTMLDialogElement.h
diff --git a/Source/core/html/HTMLDialogElement.h b/Source/core/html/HTMLDialogElement.h
index 385b96ef01270f5d17052dd3801aceaefec576fc..bc525e58cfe47d1ff7b820169f69854ea4da471e 100644
--- a/Source/core/html/HTMLDialogElement.h
+++ b/Source/core/html/HTMLDialogElement.h
@@ -43,6 +43,7 @@ public:
     void closeDialog(const String& returnValue = String());
     void show();
     void showModal(ExceptionState&);
+    bool isModal() const { return m_modal; }
 
     enum CenteringMode { Uninitialized, Centered, NotCentered };
     CenteringMode centeringMode() const { return m_centeringMode; }
@@ -62,12 +63,14 @@ private:
 
     virtual bool isPresentationAttribute(const QualifiedName&) const OVERRIDE;
     virtual void defaultEventHandler(Event*) OVERRIDE;
+    virtual void removedFrom(ContainerNode*) OVERRIDE;
 
     void forceLayoutForCentering();
 
     CenteringMode m_centeringMode;
     LayoutUnit m_centeredPosition;
     String m_returnValue;
+    bool m_modal;
 };
 
 inline bool isHTMLDialogElement(const Node& node)